Autohide fixes

Fixes: #48 (closed), #397 (closed)

Helps: #116

This MR strives to fix existing autohide bugs with as few changes as possible. In particular, we refrain from refactoring the code (unless necessary). This will be the subject of one or more future MRs when as many autohide bugs as possible have been fixed, so that non-regression can be tested under the best conditions (and it will be at least after 4.17.1 is released, or even 4.18.0).